<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>promise的race方法</title>
</head>
<body>
    
</body>
<script>
    //race()将多个promise实例包装成一个新的promise对象
    // 如果多个实例中状态都为fulfilled，那么优先执行第一个fulfilled实例
    //如果实例中有状态为rejected，不会影响整体执行，只要有fulfilled存在，就一定会走.then
    let promise1 = new Promise((resolve,reject)=>{
        setTimeout(()=>{
            resolve(1000)
        },1000)
    })

    let promise2 = new Promise((resolve,reject)=>{
        setTimeout(()=>{
            resolve('hello')
        },1000)
    })

    let promise3 = new Promise((resolve,reject)=>{
        setTimeout(()=>{
            resolve('promise3失败了')
        },1000)
    })

    let promise4 = Promise.race([promise1,promise2,promise3])
    .then((res)=>{
      console.log(res)  
    })
    .catch((err)=>{
      console.log(err)
    })
</script>
</html>